How to Update XMP Data?

Hi,

I'm using Bridge scripting to update the IPTC fields for files. I can do keywords, creator etc. However, there are some I haven't got an idea about. So for event I would have to use the namespace Iptc4xmpExt but how would I go about using it? Do I need to reference the schema?

This works for location but I can't get anything to work for Iptc4xmpExt

xmp.deleteProperty(XMPConst.NS_IPTC_CORE, "Iptc4xmpCore:Location"); 

xmp.setProperty(XMPConst.NS_IPTC_CORE, "Iptc4xmpCore:Location",Artist);